System and process for alkylation

ABSTRACT

A method for alkylating a hydrocarbon comprising at least one isoparaffin and at least one olefin that includes introducing a liquid catalyst and the hydrocarbon into a high shear device; processing the liquid catalyst and the hydrocarbon in the high shear device to form an emulsion comprising droplets of hydrocarbon dispersed in the liquid catalyst; introducing the emulsion into a vessel operating under suitable alkylation conditions whereby at least a portion of the isoparaffin is alkylated with the olefin to form alkylate, wherein suitable alkylation conditions comprise a bulk reaction temperature of from about 38° C. to about 90° C. and a bulk reaction pressure in the range of from about 1379 kPa to about 34 MPa; and removing a product stream comprising alkylate from the vessel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 12/138,240, filed Jun. 12, 2008, which applicationclaims the benefit under 35 U.S.C. §119(e) of U.S. Provisional PatentApplication No. 60/946,457 entitled “High Shear Alkylation Process,”filed Jun. 27, 2007. The disclosure of each application is herebyincorporated herein by reference in entirety for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention generally relates to alkylation. Moreparticularly, the present invention relates to a high shear system andprocess for accelerating alkylation of a feedstock comprisingisoparaffins and olefins thereby increasing the octane number of thefeedstock.

2. Background of the Invention

It is well known in the petroleum refining arts to catalytically crackheavy petroleum fractions, such as vacuum gas oil, or even in some casesatmospheric resid, in order to convert a substantial proportion thereofto a wide range of petroleum fractions. The light products fromhydrocracking are rich in isobutane. Isobutane is a primary feedstockfor motor fuel alkylation processes, which produces an excellent andenvironmentally superior gasoline-blending component.

Early alkylation units were built in conjunction with fluid catalyticcracking units to take advantage of the light end by-products of thecracking units: isoparaffins and olefins. Where the petroleum fractionbeing catalytically cracked contains sulfur, the products of catalyticcracking will also likely contain sulfur impurities. Hydrotreating isused for removal of undesirable components, including sulfur andnitrogen.

In general, hydrofinishing of FCC gasoline lowers the octane numberthereof. Smaller molecules such as isobutane and propylene or butylenescan be recombined to meet specific octane requirements of fuels byprocesses such as alkylation or less commonly, dimerization. Octanegrade of gasoline can also be improved by catalytic reforming, whichstrips hydrogen out of hydrocarbons to produce aromatics, which havemuch higher octane ratings.

Alkylation is the process of reacting light olefins with iso-butane toproduce an alkylate product high in iso-octane. In alkylation, an alkylgroup is added to an organic molecule (typically an aromatic or olefin).Thus an isoparaffin can be reacted with an olefin to provide anisoparaffin of higher molecular weight. Industrially, the conceptdepends on the reaction of a C2 to C5 olefin with isobutane in thepresence of an acidic catalyst to produce an alkylate. This alkylate isa valuable blending component in the manufacture of gasolines due to itshigh octane rating and sensitivity to octane-enhancing additives. Thismotor fuel alkylate, which is ideal for producing reformulated gasoline,is suitable for gasoline blending because of its high octane and lowvapor pressure.

Alkylate gasolines, such as those produced by the processes discussedabove, are rich in isoparaffins and contain essentially no sulfur andaromatics. Generally exhibiting strong sensitivity to octane-enhancingadditives, alkylate gasolines are prime candidates for blending intomotor gasolines to meet increasingly stringent environmental regulationsrestricting gasoline vapor pressure and aromatics content. However,these alkylate gasolines are not suitable for use as blending stocksuntil they are free from the acid components of the alkylation catalyst.Specifically, the Lewis acid component of the alkylation catalystcomplexes employed in common processes must be removed before thealkylate product can be blended into gasoline.

Standard alkylation processes have a continuous acid phase. However,U.S. Pat. No. 5,345,027 describes an alkylation process comprising aviscous acid catalyst dispersed in a continuous hydrocarbon phase.

Accordingly, there is a need in the industry for improved processes andsystems for the commercially important alkylation of isoparaffins.

SUMMARY

High shear systems and methods for enhancing isoparaffin alkylation aredisclosed. In accordance with certain embodiments a method foralkylating a hydrocarbon comprising at least one isoparaffin and atleast one olefin, the method comprising introducing liquid acid catalystand the hydrocarbon into a high shear reactor; forming an emulsioncomprising droplets comprising hydrocarbon in a continuous acid phase,wherein the droplets have a mean diameter of less than about 5 μm;introducing the emulsion into a vessel operating under suitablealkylation conditions whereby at least a portion of the isoparaffin isalkylated with the olefin to form alkylate; and removing a productstream comprising alkylate from the vessel. The isoparaffin may containfrom 4 to 8 carbon atoms. The olefin may contain from 2 to 12 carbonatoms. In embodiments, the at least one isoparaffin comprises isobutaneand the at least one olefin comprises butene. Suitable alkylationconditions may comprise a temperature of from about 0° C. to about 90°C. and a pressure in the range of from about 345 kPa to about 3447 kPa.The catalyst may comprise an acid selected from sulfuric acid,hydrofluoric acid, BF₃, SbF₅, and AlCl₃. The droplets in the emulsionmay have a mean diameter of less than 400 nm, or no more than 100 nm.Forming the emulsion may comprise subjecting the hydrocarbon and acid tohigh shear mixing at a tip speed of at least 22.9 m/s, or at least 40m/s. The high shear mixing may produce a local pressure of at leastabout 1034 MPa at the tip. Forming the emulsion may comprise subjectinga mixture comprising the hydrocarbon and the acid to a shear rate ofgreater than about 20,000 s⁻¹. In embodiments, forming the emulsioncomprises an energy expenditure of at least 1000 W/m³. The alkylationmay occur at a velocity at least 5 fold greater than that of a similarmethod wherein the hydrocarbon and liquid acid catalyst are notsubjected to high shear mixing.

Also disclosed is a system for the alkylation of a hydrocarboncomprising at least one isoparaffin and at least one olefin, the systemcomprising at least one external high shear mixing device comprising atleast one rotor and at least one stator separated by a shear gap,wherein the shear gap is the minimum distance between the at least onerotor and the at least stator, and wherein the high shear mixing deviceis capable of producing a tip speed at the tip of the at least one rotorof greater than 22.9 m/s (4,500 ft/min), a pump configured fordelivering a pressurized liquid stream comprising liquid acid catalystto the at least one high shear mixing device; and a vessel configuredfor receiving an emulsion from the high shear mixing device. The sheargap may be in the range of from about 0.02 mm to about 5 mm. The highshear mixing device may be configured to produce an emulsion comprisingdroplets having a mean diameter of less than 1 micron, wherein theemulsion comprises hydrocarbon droplets dispersed in a continuous liquidphase comprising acid catalyst or wherein the emulsion comprisesdroplets comprising acid catalyst in a continuous liquid phasecomprising hydrocarbon. The at least one high shear mixing device may beconfigured for operating at a flow rate of at least 300 L/h. The atleast one high shear mixing device may be configured to provide anenergy expenditure greater than 1000 W/m³. In embodiments, the at leastone high shear mixing device comprises at least two rotors and at leasttwo stators.

The process employs an external high shear mechanical reactor to provideenhanced time, temperature and pressure conditions resulting inaccelerated chemical reactions between multiphase reactants.

In some embodiments, the system further comprises a pump configured fordelivering a liquid stream comprising acid catalyst to the high shearmixing device. In some embodiments, the system further comprises avessel configured for receiving the emulsion from the high shear device.Some embodiments of the system potentially make possible the alkylationof feedstock without the need for large volume reactors, via use of anexternal pressurized high shear reactor.

Embodiments of the disclosure pertain to a method for alkylating ahydrocarbon comprising at least one isoparaffin and at least one olefinthat may include introducing a liquid catalyst and the hydrocarbon intoa high shear device; processing the liquid catalyst and the hydrocarbonin the high shear device to form an emulsion comprising droplets ofhydrocarbon dispersed in the liquid catalyst; introducing the emulsioninto a vessel operating under suitable alkylation conditions whereby atleast a portion of the isoparaffin is alkylated with the olefin to formalkylate, wherein suitable alkylation conditions comprise a bulkreaction temperature of from about 38° C. to about 90° C. and a bulkreaction pressure in the range of from about 1379 kPa to about 34 MPa;and removing a product stream comprising alkylate from the vessel.

The at least one isoparaffin may contain from 4 to 8 carbon atoms. Theat least one olefin may contain from 2 to 12 carbon atoms. In aspects,the at least one isoparaffin may be isobutane and the at least oneolefin may be butene. The liquid catalyst may include an acid selectedfrom hydrofluoric acid, BF₃, SbF₅, and AlCl₃. In aspects, the dropletsmay have a mean diameter of no more than 100 nm.

In forming the emulsion, the method may also include subjecting thehydrocarbon and acid to high shear mixing at a tip speed of at least22.9 m/s and to a shear rate of greater than about 20,000 s⁻¹. The highshear device may produce a local pressure of at least about 1034 MPa atthe tip. The high shear device may include a rotor and a statorseparated by a shear gap. The droplets may have a mean diameter in therange of about 0.1 μm to about 5 μm. The shear gap may have a width inthe range of from about 0.02 mm to about 5 mm. The rotor and/or thestator may be configured with at least one toothed surface.

Other aspects of the disclosure pertain to a method for alkylating ahydrocarbon comprising at least one isoparaffin and at least one olefinthat may include introducing a liquid catalyst selected from the groupconsisting of hydrofluoric acid, BF₃, SbF₅, AlCl₃, and combinationsthereof, and the hydrocarbon into a high shear device; processing theliquid catalyst and the hydrocarbon in the high shear device to form anemulsion comprising droplets having a mean diameter less than about 5μm; and transferring the emulsion from the high shear device into avessel operating under suitable alkylation conditions whereby at least aportion of the isoparaffin is alkylated with the olefin to formalkylate.

The at least one isoparaffin may have from 4 to 8 carbon atoms. The atleast one olefin may have from 2 to 12 carbon atoms. The method mayfurther include removing a product stream comprising alkylate from thevessel. In aspects, the droplets may have a mean diameter of no morethan 100 nm.

The high shear device may include a rotor and a stator separated by ashear gap in the range of from about 0.02 mm to about 5 mm. The rotorand/or the stator may include at least one toothed surface. In aspects,the emulsion may include hydrocarbon droplets dispersed in the liquidcatalyst, wherein the mean diameter is less than 1 micron. In otheraspects, the emulsion may include catalyst droplets dispersed in thehydrocarbon, wherein the mean diameter is less than 1 micron. In yetother aspects, the mean diameter may also be greater than about 0.1 μm.

In still other embodiments, the present disclosure pertains to a methodfor alkylating a hydrocarbon comprising at least one isoparaffin and atleast one olefin that may include introducing a liquid catalyst and thehydrocarbon into a high shear device, wherein the liquid catalystcomprises an acid selected from the group consisting of sulfuric acid,hydrofluoric acid, BF₃, SbF₅, AlCl₃, and combinations thereof; formingan emulsion comprising hydrocarbon droplets dispersed in the liquidcatalyst, wherein the droplets have a mean diameter of less than about 5μm; and introducing the emulsion into a vessel operating under suitablealkylation conditions whereby at least a portion of the isoparaffin isalkylated with the olefin to form alkylate, wherein suitable alkylationconditions comprise a bulk reaction temperature of from about 38° C. toabout 90° C. and a bulk reaction pressure in the range of from about1379 kPa to about 34 MPa. In aspects, the mean diameter may also begreater than about 0.1 μm.

Certain embodiments of an above-described method or system potentiallyprovide for more optimal time, temperature and pressure conditions thanare otherwise possible, and which potentially increase the rate of theliquid/liquid or liquid/liquid/solid phase process. Certain embodimentsof the above-described methods or systems potentially provide overallcost reduction by operating at lower temperature and/or pressure,providing increased product per unit of catalyst consumed, decreasedreaction time, decreased olefin excess used, and/or reduced capitaland/or operating costs. These and other embodiments and potentialadvantages will be apparent in the following detailed description anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more detailed description of the preferred embodiment of thepresent invention, reference will now be made to the accompanyingdrawings, wherein:

FIG. 1 is a process flow diagram of an alkylation system according to anembodiment of the present disclosure comprising external high sheardispersing.

FIG. 2 is a longitudinal cross-section view of a multi-stage high sheardevice, as employed in an embodiment of the system.

NOTATION AND NOMENCLATURE

As used herein, the term “dispersion” refers to a liquefied mixture thatcontains at least two distinguishable substances (or “phases”) that willnot readily mix and dissolve together. As used herein, a “dispersion”comprises a “continuous” phase (or “matrix”), which holds thereindiscontinuous droplets, bubbles, and/or particles of the other phase orsubstance. The term dispersion may thus refer to foams comprising gasbubbles suspended in a liquid continuous phase, emulsions in whichdroplets of a first liquid are dispersed throughout a continuous phasecomprising a second liquid with which the first liquid is immiscible,and continuous liquid phases throughout which solid particles aredistributed. As used herein, the term “dispersion” encompassescontinuous liquid phases throughout which gas bubbles are distributed,continuous liquid phases throughout which solid particles (e.g., solidcatalyst) are distributed, continuous phases of a first liquidthroughout which droplets of a second liquid that is substantiallyinsoluble in the continuous phase are distributed, and liquid phasesthroughout which any one or a combination of solid particles, immiscibleliquid droplets, and gas bubbles are distributed. Hence, a dispersioncan exist as a homogeneous mixture in some cases (e.g., liquid/liquidphase), or as a heterogeneous mixture (e.g., gas/liquid, solid/liquid,or gas/solid/liquid), depending on the nature of the materials selectedfor combination.

DETAILED DESCRIPTION Overview

The present processes and systems for alkylation via liquid phasereaction of isoparaffins and olefins with acid catalyst comprises anexternal high shear mechanical device to provide rapid contact andmixing of the chemical ingredients in a controlled environment in a highshear mixing device, which may also serve as a reactor. The high sheardevice reduces the mass transfer limitations on the reaction and thusincreases the overall reaction rate.

The alkylation of isoparaffin (e.g., isobutane) with low molecularweight alkenes (e.g., propylene and butylene) in the presence ofcatalyst (e.g., strong acid catalyst such as sulfuric acid orhydrofluoric acid) is a multiphase reaction. The two phases separatespontaneously without agitation. The presently disclosed method andsystem whereby the acid phase is intimately mixed with the hydrocarbonphase to form an emulsion enhances contact surface between the reactioncomponents, thus enhancing the reaction. The disclosed high shear systemand method may be incorporated into conventional alkylation process,thereby enhancing yield of alkylated isoparaffin, reducing catalystrequirements (and thereby also minimizing downstream catalyst removal),and/or permitting the use of decreased amounts of excess isoparaffin inthe feed.

The rate of chemical reactions involving liquids, gases and solidsdepend on time of contact, temperature, and pressure. In cases where itis desirable to react two or more raw materials of different phases(e.g. solid and liquid; liquid and gas; solid, liquid and gas), one ofthe limiting factors controlling the rate of reaction involves thecontact time of the reactants. In the case of heterogeneously catalyzedreactions there is the additional rate limiting factor of having thereacted products removed from the surface of the catalyst to permit thecatalyst to catalyze further reactants. Contact time for the reactantsand/or catalyst is often controlled by mixing which provides contactwith two or more reactants involved in a chemical reaction. Homogeneousreactions (e.g., liquid-liquid phase) may also benefit from high shearmixing, as disclosed herein, by at least providing uniform temperaturedistribution within the reactor and minimizing potential side reactions.Accordingly, in some embodiments, a high shear process as describedherein promotes homogeneous reaction(s).

A reactor assembly that comprises an external high shear device or mixeras described herein makes possible decreased mass transfer limitationsand thereby allows the reaction to more closely approach kineticlimitations. When reaction rates are accelerated, residence times may bedecreased, thereby increasing obtainable throughput. Product yield maybe increased as a result of the high shear system and process.Alternatively, if the alkylate yield of an existing process isacceptable, decreasing the required residence time by incorporation ofsuitable high shear may allow for the use of lower temperatures and/orpressures, increased alkylate product per unit of catalyst consumed,and/or the use of a reduced excess of olefin than conventionalprocesses.

Furthermore, without wishing to be limited by theory, it is believedthat the high shear conditions provided by a reactor assembly thatcomprises an external high shear device or mixer as described herein maypermit alkylation at global operating conditions under which reactionmay not conventionally be expected to occur to any significant extent.Although the discussion of the system and method will be made withreference to alkylation of isoparaffins, it is to be understood that thedisclosed system and method may also be applicable to other alkylationsand acylations.

System for Alkylation. A high shear alkylation system will now bedescribed in relation to FIG. 1, which is a process flow diagram of anembodiment of a high shear system 100 for alkylation of feedstockcomprising isoparaffin with low molecular weight alkene (e.g., propeneand butane) by liquid phase reaction in the presence of a strong acidcatalyst (e.g., sulfuric acid or hydrofluoric acid). It should be notedthat FIG. 1 is a simplified process diagram and many pieces of processequipment, such as separators, heaters and compressors, have beenomitted for clarity. The basic components of a representative systeminclude external high shear mixing device (HSD) 40, vessel 10, and pump5. As shown in FIG. 1, high shear device 40 is located external tovessel/reactor 10. Each of these components is further described in moredetail below. Line 21 is connected to pump 5 for introducing a liquidstream comprising liquid acid catalyst. Line 13 connects pump 5 to HSD40, and line 18 connects HSD 40 to vessel 10. Line 22 may be connectedto line 13 for introducing a feedstream comprising isoparaffin to bealkylated and alkene. Alternatively, in embodiments, line 22 may beconnected to an inlet of HSD 40 or introduced into line 21. Line 17 maybe connected to vessel 10 for removal of vent gas containing unreactedhydrocarbon vapor and any other reaction gases. Additional components orprocess steps may be incorporated between vessel 10 and HSD 40, or aheadof pump 5 or HSD 40, if desired, as will become apparent upon readingthe description of the high shear alkylation process describedhereinbelow.

For example, line 38 may be connected to line 13 or line 21 from adownstream location (e.g., line 39 from settler 30), to provide formulti-pass operation, if desired.

High Shear Mixing Device. External high shear mixing device (HSD) 40,also sometimes referred to as a high shear device or high shear mixingdevice, is configured for receiving an inlet stream, via line 13,comprising hydrocarbon feed and concentrated acid catalyst.Alternatively, HSD 40 may be configured for receiving the liquidcatalyst and the liquid hydrocarbon via separate inlet lines (notshown). Although only one high shear device is shown in FIG. 1, itshould be understood that some embodiments of the system may have two ormore high shear mixing devices arranged either in series or parallelflow. HSD 40 is a mechanical device that utilizes one or more generatorcomprising a rotor/stator combination, each of which has a gap betweenthe stator and rotor. The gap between the rotor and the stator in eachgenerator set may be fixed or may be adjustable. HSD 40 is configured insuch a way that it is capable of producing an emulsion containingsubmicron (i.e., less than one micron in diameter) and/or micron-sizedparticles containing hydrocarbon dispersed in a continuous acid phaseflowing through the high shear device. The high shear device comprisesan enclosure or housing so that the pressure and temperature of thereaction mixture may be controlled.

High shear mixing devices are generally divided into three generalclasses, based upon their ability to mix fluids. Mixing is the processof reducing the size of particles or inhomogeneous species within thefluid. One metric for the degree or thoroughness of mixing is the energydensity per unit volume that the mixing device generates to disrupt thefluid particles. The classes are distinguished based on delivered energydensities. Three classes of industrial mixers having sufficient energydensity to consistently produce mixtures or emulsions with droplet sizesin the range of submicron to 50 microns include homogenization valvesystems, colloid mills and high speed mixers. In the first class of highenergy devices, referred to as homogenization valve systems, fluid to beprocessed is pumped under very high pressure through a narrow-gap valveinto a lower pressure environment. The pressure gradients across thevalve and the resulting turbulence and cavitation act to break-up anyparticles in the fluid. These valve systems are most commonly used inmilk homogenization and can yield average droplet (globule) sizes in thesubmicron to about 1 micron range.

At the opposite end of the energy density spectrum is the third class ofdevices referred to as low energy devices. These systems usually havepaddles or fluid rotors that turn at high speed in a reservoir of fluidto be processed, which in many of the more common applications is a foodproduct. These low energy systems are customarily used when averageparticle sizes of greater than 20 microns are acceptable in theprocessed fluid.

Between the low energy devices and homogenization valve systems, interms of the mixing energy density delivered to the fluid, are colloidmills and other high speed rotor-stator devices, which are classified asintermediate energy devices. A typical colloid mill configurationincludes a conical or disk rotor that is separated from a complementary,liquid-cooled stator by a closely-controlled rotor-stator gap, which iscommonly between 0.0254 mm to 10.16 mm (0.001-0.40 inch). Rotors areusually driven by an electric motor through a direct drive or beltmechanism. As the rotor rotates at high rates, it pumps fluid betweenthe outer surface of the rotor and the inner surface of the stator, andshear forces generated in the gap process the fluid. Many colloid millswith proper adjustment achieve average particle sizes of 0.1-25 micronsin the processed fluid. These capabilities render colloid millsappropriate for a variety of applications including colloid andoil/water-based emulsion processing such as that required for cosmetics,mayonnaise, or silicone/silver amalgam formation, to roofing-tar mixing.

Tip speed is the circumferential distance traveled by the tip of therotor per unit of time. Tip speed is thus a function of the rotordiameter and the rotational frequency. Tip speed (in meters per minute,for example) may be calculated by multiplying the circumferentialdistance transcribed by the rotor tip, 2πR, where R is the radius of therotor (meters, for example) times the frequency of revolution (forexample revolutions per minute, rpm). A colloid mill, for example, mayhave a tip speed in excess of 22.9 m/s (4500 ft/min) and may exceed 40m/s (7900 ft/min) For the purpose of this disclosure, the term ‘highshear’ refers to mechanical rotor stator devices (e.g., colloid mills orrotor-stator dispersers) that are capable of tip speeds in excess of 5.1m/s. (1000 ft/min) and require an external mechanically driven powerdevice to drive energy into the stream of products to be reacted. Forexample, in HSD 40, a tip speed in excess of 22.9 m/s (4500 ft/min) isachievable, and may exceed 40 m/s (7900 ft/min). In some embodiments,HSD 40 is capable of delivering at least 300 L/h at a tip speed of atleast 22.9 m/s (4500 ft/min) The power consumption may be about 1.5 kW.

HSD 40 combines high tip speed with a very small shear gap to producesignificant shear on the material being processed. The amount of shearwill be dependent on the viscosity of the fluid. Accordingly, a localregion of elevated pressure and temperature is created at the tip of therotor during operation of the high shear device. In some cases thelocally elevated pressure is about 1034.2 MPa (150,000 psi). In somecases the locally elevated temperature is about 500° C. In some cases,these local pressure and temperature elevations may persist for nano orpico seconds.

An approximation of energy input into the fluid (kW/L/min) can beestimated by measuring the motor energy (kW) and fluid output (L/min) Asmentioned above, tip speed is the velocity (ft/min or m/s) associatedwith the end of the one or more revolving elements that is creating themechanical force applied to the reactants. In embodiments, the energyexpenditure of HSD 40 is greater than 1000 W/m³. In embodiments, theenergy expenditure of HSD 40 is in the range of from about 3000 W/m³ toabout 7500 W/m³.

The shear rate is the tip speed divided by the shear gap width (minimalclearance between the rotor and stator). The shear rate generated in HSD40 may be in the greater than 20,000 s⁻¹. In some embodiments the shearrate is at least 40,000 s⁻¹. In some embodiments the shear rate is atleast 100,000 s⁻¹. In some embodiments the shear rate is at least500,000 s⁻¹. In some embodiments the shear rate is at least 1,000,000s⁻¹. In some embodiments the shear rate is at least 1,600,000 s⁻¹. Inembodiments, the shear rate generated by HSD 40 is in the range of from20,000 s⁻¹ to 100,000 s⁻¹. For example, in one application the rotor tipspeed is about 40 m/s (7900 ft/min) and the shear gap width is 0.0254 mm(0.001 inch), producing a shear rate of 1,600,000 s⁻¹. In anotherapplication the rotor tip speed is about 22.9 m/s (4500 ft/min) and theshear gap width is 0.0254 mm (0.001 inch), producing a shear rate ofabout 901,600 s⁻¹.

HSD 40 is capable of highly emulsifying hydrocarbon into a main liquidphase comprising acid with which the hydrocarbon would normally beimmiscible, at conditions such that at least a portion of the smallolefins and isoparaffins are converted into larger isoparaffins with ahigh octane number. Although not discussed in detail herein, it isunderstood that, in embodiments, a viscous acid phase may be utilized,and, in such cases, HSD 40 may be used to form an emulsion comprisingviscous acid catalyst dispersed in a continuous hydrocarbon phase. Thus,in embodiments, the continuous phase comprises acid catalyst. Inalternative embodiments, the continuous phase comprises hydrocarbon.

In embodiments, the emulsion further comprises a solid particulatecatalyst. In some embodiments, HSD 40 comprises a colloid mill. Suitablecolloidal mills are manufactured by IKA® Works, Inc. Wilmington, N.C.and APV North America, Inc. Wilmington, Mass., for example. In someinstances, HSD 40 comprises the Dispax Reactor® of IKA® Works, Inc.

The high shear device comprises at least one revolving element thatcreates the mechanical force applied to the reactants. The high sheardevice comprises at least one stator and at least one rotor separated bya clearance. For example, the rotors may be conical or disk shaped andmay be separated from a complementarily-shaped stator. In embodiments,both the rotor and stator comprise a plurality ofcircumferentially-spaced teeth. In some embodiments, the stator(s) areadjustable to obtain the desired shear gap between the rotor and thestator of each generator (rotor/stator set). Grooves between the teethof the rotor and/or stator may alternate direction in alternate stagesfor increased turbulence. Each generator may be driven by any suitabledrive system configured for providing the necessary rotation.

In some embodiments, the minimum clearance (shear gap width) between thestator and the rotor is in the range of from about 0.0254 mm (0.001inch) to about 3.175 mm (0.125 inch). In certain embodiments, theminimum clearance (shear gap width) between the stator and rotor isabout 1.52 mm (0.060 inch). In certain configurations, the minimumclearance (shear gap) between the rotor and stator is at least 1.78 mm(0.07 inch). The shear rate produced by the high shear device may varywith longitudinal position along the flow pathway. In some embodiments,the rotor is set to rotate at a speed commensurate with the diameter ofthe rotor and the desired tip speed. In some embodiments, the high sheardevice has a fixed clearance (shear gap width) between the stator androtor. Alternatively, the high shear device has adjustable clearance(shear gap width).

In some embodiments, HSD 40 comprises a single stage dispersing chamber(i.e., a single rotor/stator combination, a single generator). In someembodiments, high shear device 40 is a multiple stage inline disperserand comprises a plurality of generators. In certain embodiments, HSD 40comprises at least two generators. In other embodiments, high sheardevice 40 comprises at least 3 high shear generators. In someembodiments, high shear device 40 is a multistage mixer whereby theshear rate (which, as mentioned above, varies proportionately with tipspeed and inversely with rotor/stator gap width) varies withlongitudinal position along the flow pathway, as further describedherein below.

In some embodiments, each stage of the external high shear device hasinterchangeable mixing tools, offering flexibility. For example, the DR2000/4 Dispax Reactor® of IKA® Works, Inc. Wilmington, N.C. and APVNorth America, Inc. Wilmington, Mass., comprises a three stagedispersing module. This module may comprise up to three rotor/statorcombinations (generators), with choice of fine, medium, coarse, andsuper-fine for each stage. This allows for creation of emulsions havinga narrow distribution of the desired droplet size (e.g., hydrocarbondroplets). In some embodiments, each of the stages is operated withsuper-fine generator. In some embodiments, at least one of the generatorsets has a rotor/stator minimum clearance (shear gap width) of greaterthan about 5.08 mm (0.20 inch). In alternative embodiments, at least oneof the generator sets has a minimum rotor/stator clearance of greaterthan about 1.78 mm (0.07 inch).

Referring now to FIG. 2, there is presented a longitudinal cross-sectionof a suitable high shear device 200. High shear device 200 of FIG. 2 isa dispersing device comprising three stages or rotor-statorcombinations. High shear device 200 is a dispersing device comprisingthree stages or rotor-stator combinations, 220, 230, and 240. Therotor-stator combinations may be known as generators 220, 230, 240 orstages without limitation. Three rotor/stator sets or generators 220,230, and 240 are aligned in series along drive shaft 250.

First generator 220 comprises rotor 222 and stator 227. Second generator230 comprises rotor 223, and stator 228. Third generator 240 comprisesrotor 224 and stator 229. For each generator the rotor is rotatablydriven by input 250 and rotates about axis 260 as indicated by arrow265. The direction of rotation may be opposite that shown by arrow 265(e.g., clockwise or counterclockwise about axis of rotation 260).Stators 227, 228, and 229 are fixably coupled to the wall 255 of highshear device 200.

As mentioned hereinabove, each generator has a shear gap width which isthe minimum distance between the rotor and the stator. In the embodimentof FIG. 2, first generator 220 comprises a first shear gap 225; secondgenerator 230 comprises a second shear gap 235; and third generator 240comprises a third shear gap 245. In embodiments, shear gaps 225, 235,245 have widths in the range of from about 0.025 mm to about 10.0 mm.Alternatively, the process comprises utilization of a high shear device200 wherein the gaps 225, 235, 245 have a width in the range of fromabout 0.5 mm to about 2.5 mm. In certain instances the shear gap widthis maintained at about 1.5 mm. Alternatively, the width of shear gaps225, 235, 245 are different for generators 220, 230, 240. In certaininstances, the width of shear gap 225 of first generator 220 is greaterthan the width of shear gap 235 of second generator 230, which is inturn greater than the width of shear gap 245 of third generator 240. Asmentioned above, the generators of each stage may be interchangeable,offering flexibility. High shear device 200 may be configured so thatthe shear rate will increase stepwise longitudinally along the directionof the flow 260.

Generators 220, 230, and 240 may comprise a coarse, medium, fine, andsuper-fine characterization. Rotors 222, 223, and 224 and stators 227,228, and 229 may be toothed designs. Each generator may comprise two ormore sets of rotor-stator teeth. In embodiments, rotors 222, 223, and224 comprise more than 10 rotor teeth circumferentially spaced about thecircumference of each rotor. In embodiments, stators 227, 228, and 229comprise more than ten stator teeth circumferentially spaced about thecircumference of each stator. In embodiments, the inner diameter of therotor is about 12 cm. In embodiments, the diameter of the rotor is about6 cm. In embodiments, the outer diameter of the stator is about 15 cm.In embodiments, the diameter of the stator is about 6.4 cm. In someembodiments the rotors are 60 mm and the stators are 64 mm in diameter,providing a clearance of about 4 mm. In certain embodiments, each ofthree stages is operated with a super-fine generator, comprising a sheargap of between about 0.025 mm and about 4 mm. For applications in whichsolid particles are to be sent through high shear device 40, theappropriate shear gap width (minimum clearance between rotor and stator)may be selected for an appropriate reduction in particle size andincrease in particle surface area. In embodiments, this may bebeneficial for increasing catalyst surface area by shearing anddispersing the particles.

High shear device 200 is configured for receiving from line 13 areactant stream at inlet 205. The reaction mixture comprises acidcatalyst as the dispersible phase and hydrocarbon liquid as thecontinuous phase. The feed stream may further comprise a particulatesolid catalyst component. Feed stream entering inlet 205 is pumpedserially through generators 220, 230, and then 240, such that productemulsion is formed. Product emulsion exits high shear device 200 viaoutlet 210 (and line 18 of FIG. 1). The rotors 222, 223, 224 of eachgenerator rotate at high speed relative to the fixed stators 227, 228,229, providing a high shear rate. The rotation of the rotors pumpsfluid, such as the feed stream entering inlet 205, outwardly through theshear gaps (and, if present, through the spaces between the rotor teethand the spaces between the stator teeth), creating a localized highshear condition. High shear forces exerted on fluid in shear gaps 225,235, and 245 (and, when present, in the gaps between the rotor teeth andthe stator teeth) through which fluid flows process the fluid and createproduct emulsion. Product emulsion exits high shear device 200 via highshear outlet 210 (and line 18 of FIG. 1).

The product emulsion comprising droplets, in a continuous liquid phasemay be referred to as an dispersion or an emulsion herein. The productemulsion has an average droplet size less than about 5 μm. Inembodiments, HSD 40 produces an emulsion having a mean droplet size ofless than about 1.5 μm. In embodiments, HSD 40 produces an emulsionhaving a mean droplet size of less than 1 μm; preferably the dropletsare sub-micron in diameter. In certain instances, the average dropletsize is from about 0.1 μm to about 1.0 μm. In embodiments, HSD 40produces an emulsion having a mean droplet size of less than 400 nm. Inembodiments, HSD 40 produces an emulsion having a mean droplet size ofless than 100 nm. High shear device 200 produces an emulsion comprisingdispersed droplets capable of remaining dispersed at atmosphericpressure for at least about 10 minutes or at least about 15 minutes.

In certain instances, high shear device 200 comprises a Dispax Reactor®of IKA® Works, Inc. Wilmington, N.C. and APV North America, Inc.Wilmington, Mass. Several models are available having variousinlet/outlet connections, horsepower, tip speeds, output rpm, and flowrate. Selection of the high shear device will depend on throughputrequirements and desired droplet or globule size in the emulsion in line18 (FIG. 1) exiting outlet 210 of high shear device 200. IKA® model DR2000/4, for example, comprises a belt drive, 4M generator, PTFE sealingring, inlet flange 25.4 mm (1 inch) sanitary clamp, outlet flange 19 mm(¾ inch) sanitary clamp, 2HP power, output speed of 7900 rpm, flowcapacity (water) approximately 300-700 L/h (depending on generator), atip speed of from 9.4-41 m/s (1850 ft/min to 8070 ft/min).

Vessel. The emulsion in line 18 enters reactor 10 wherein alkylationcontinues. Vessel or reactor 10 is any type of vessel in which themultiphase alkylation reaction can be propagated. Vessel 10 may be anysuitable vessel, for example, a continuous stirred tank reactor such asthat typically employed in sulfuric acid alkylation or a tubularriser-type reactor such as is typically used for hydrofluoric acidalkylation. Vessel 10 may be, for instance, a continuous orsemi-continuous stirred tank reactor, or one or more batch reactors maybe employed in series or in parallel. In some applications vessel 10 maybe a tower reactor, and in others a tubular reactor or multi-tubularreactor. One or more line 15 may be connected to vessel 10 forintroducing the acid catalyst, or for injecting water, or other material(e.g., a solid catalyst).

Alkylation reactions will occur whenever suitable time, temperature andpressure conditions exist. In this sense alkylation could occur at anypoint in the flow diagram of FIG. 1 if temperature and pressureconditions are suitable.

Vessel 10 may include one or more of the following components: stirringsystem, temperature control capabilities, pressure measurementinstrumentation, temperature measurement instrumentation, one or moreinjection points, and level regulator (not shown), as are known in theart of reaction vessel design. For example, a stirring system mayinclude a motor driven mixer 3, as indicated in FIG. 1. A temperaturecontrol apparatus may comprise, for example, a heat exchanger.Alternatively, as much of the alkylation may occur within HSD 40 in someembodiments, vessel 10 may serve primarily as a storage vessel in somecases. Although generally less desired, in some applications vessel 10may be omitted, particularly if multiple high shear devices/reactors areemployed in series, as further described below.

Line 16 is connected to vessel 10 for withdrawal or removal of reactionproduct containing alkylate. In some embodiments, a separating tank 30may be connected to vessel 10 by line 16, for separation of hydrocarbonfrom acid catalyst, which may be recycled to HSD 40, if desired. Line 17may be connected to vessel 10 for removal of vent gas. In embodiments,vessel 10 comprises a plurality of reactor product lines 16.

Heat Transfer Devices. In addition to the above-mentionedheating/cooling capabilities of vessel 10, other external or internalheat transfer devices for heating or cooling a process stream are alsocontemplated in variations of the embodiments illustrated in FIG. 1. Forexample, if the reaction is exothermic, reaction heat may be removedfrom vessel 10 via any method known to one skilled in the art. The useof external heating and/or cooling heat transfer devices is alsocontemplated. Some suitable locations for one or more such heat transferdevices are between pump 5 and HSD 40, between HSD 40 and vessel 10, andbetween vessel 10 and pump 5 when system 100 is operated in multi-passmode. Some non-limiting examples of such heat transfer devices areshell, tube, plate, and coil heat exchangers, as are known in the art.

Pumps. Pump 5 is configured for either continuous or semi-continuousoperation, and may be any suitable pumping device that is capable ofproviding greater than 202.65 kPa (2 atm) pressure, preferably greaterthan 303.975 kPa (3 atm) pressure, to allow controlled flow through HSD40 and system 100. For example, a Roper Type 1 gear pump, Roper PumpCompany (Commerce Ga.) Dayton Pressure Booster Pump Model 2P372E, DaytonElectric Co (Niles, Ill.) is one suitable pump. Preferably, all contactparts of the pump comprise stainless steel, or, when corrosivesubstances such as concentrated acid will be pumped, the contactsurfaces may be gold plated. In some embodiments of the system, pump 5is capable of pressures greater than about 2026.5 kPa (20 atm). Inaddition to pump 5, one or more additional, high pressure pump (notshown) may be included in the system illustrated in FIG. 1. For example,a booster pump, which may be similar to pump 5, may be included betweenHSD 40 and vessel 10 for boosting the pressure into vessel 10. Asanother example, a supplemental feed pump, which may be similar to pump5, may be included for introducing the strong acid, water, or additionalreactants or a solid catalyst into vessel 10. Although not shown in FIG.1, an outlet line may connect vessel 10 to line 21 for introducing acidcatalyst into HSD 40 via pump 5 and line 13.

Alkylation Process. Operation of high shear alkylation system 100 willnow be discussed with reference to FIG. 1. In operation for thealkylation of hydrocarbon streams comprising isoparaffin, a dispersiblehydrocarbon feed stream is introduced into system 100 via line 22, andcombined in line 13 with a liquid stream in line 21 comprising acidcatalyst.

Hydrocarbon feedstream introduced in line 22 comprises at least anolefin and a paraffin to be alkylated. In embodiments, the isoparaffinreactant used in the present alkylation process contains from about 4 toabout 8 carbon atoms. Representative examples of such isoparaffinsinclude isobutane, isopentane, 3-methylhexane, 2-methylhexane,2,3-dimethylbutane and 2,4-dimethylhexane. In embodiments, theisoparaffin is isobutene. The olefin component of the feedstock includesat least one olefin having from 2 to 12 carbon atoms. Representativeexamples of such olefins include butene-2, isobutylene, butene-1,propylene, ethylene, hexene, octene, and heptene, for example. The mostpreferred olefins may be C3 and C4 olefins, for example, propylene,butene-1, butene-2, isobutylene, or a mixture of two or more of theseolefins. In embodiments, the hydrocarbon feedstream in line 22 comprisesan olefin selected from propylene, butylenes, pentylenes, andcombinations thereof. In embodiments, hydrocarbon feedstream in line 22comes from a fluidized catalytic cracking unit.

The ratio of isoparaffin to olefin is conventionally kept high duringalkylation of isoparaffins to prevent/minimize side reactions that mayreduce the octane rating of the product. In embodiments, the overallmolar ratio of isoparaffin to olefin in the hydrocarbon feed is in therange of from 1:1 and 100:1, preferably between about 5:1 and about20:1. Use of the disclosed high shear system and method may permitalkylation at lower isoparaffin to olefin ratio than conventional.

In embodiments, the catalyst is a liquid catalyst. In embodiments, thecatalyst is a solid catalyst. In embodiments, the catalyst is acombination of liquid and solid phase catalyst. In embodiments,dispersible reactant in line 21 comprises liquid acid catalyst.

In embodiments, dispersible catalyst in line 21 comprises a Bronstedacid. In embodiments, catalyst line 21 comprises a Bronsted acidselected from hydrofluoric acid and sulfuric acid. As both hydrofluoricand sulfuric acid catalysts are gradually depleted in continuousalkylation, fresh acid may be continuously introduced into line 21 tomaintain acid strength, reaction rate, and the resulting alkylatequality. Alkylate quality is affected by acid strength, and fresh acidmakeup and/or regeneration rate may be controlled together with otherprocess variables such as temperature and space velocity, to meet arequired alkylate quality specification. Typically, more concentratedacid catalysts maximize yield of isoparaffins and suppress undesirableolefin oligomerization side reactions. In embodiments, catalyst line 21comprises a Lewis acid. The Lewis acid may comprise BF₃ or BF₃:H₃PO₄adducts.

Acid strength in these liquid acid catalyzed alkylation processes ispreferably maintained at 88 to 94 weight percent by the continuousaddition of fresh acid in line 21 and the continuous withdrawal of spentacid. In embodiments, spent acid is removed from high shear system 100via spent acid line 38, a portion of which may be recycled to high sheardevice 40 via, for example, introduction into acid line 21 via acidrecycle line 39. Acid recycled to HSD 40 via line 21 may undergo furthertreatment prior to reintroduction into HSD 40. In embodiments, freshcatalyst enters high shear system 100 upstream of high shear device 40.In embodiments, fresh acid catalyst is introduced to high shearalkylation system 100 via inlet line 15. In embodiments, spend acid isremoved from high shear system 100 via spent acid line 37.

In embodiments, high shear system 100 comprises a suitable solidcatalyst as disclosed in the art. In embodiments, the alkylationreaction carried out by high shear process 100 is a heterogeneouscatalytic reaction involving a solid catalyst. In embodiments wherein asolid catalyst is utilized, reactor 10 may comprise, for example, afixed or a slurry bed. In embodiments, reactor 10 comprises a solidcatalyst. For example, in embodiments, the catalyst comprises one ormore transitional aluminas which are treated with at least one Lewisacid, preferably BF₃. The process may also utilize an amount of freeLewis acid and to produce high octane alkylate. In embodiments, thesolid catalyst comprises a large pore zeolite ZSM-4, ZSM-20, ZSM-3,ZSM-18, zeolite Beta, faujasite, mordenite, zeolite Y and the rare earthmetal-containing forms of zeolite Y, and a Lewis acid such as BF₃, SbF₅,or AlCl₃. In embodiments, the catalyst comprises Lewis acid and a solidcomponent comprising a layered silicate and pillars of an oxideseparating the layers of the silicate. A suitable solid catalyst mayinclude acidic zeolites, alumina, silica-alumina, silica, boron oxides,phosphorus oxides, titanium oxide, zirconium oxide, chromia, zinc oxide,magnesia, calcium oxide, silica-alumina-zirconia, chromia-alumina,alumina-boria, silica-zirconia, aluminum phosphate molecular sieves,silicoaluminophosphate molecular sieves, solid polymeric ion exchangeresins, tetravalent metal phosphonates with pendent acid groups,sulfated metal oxides (such as alumina), and the like. These catalystsmay be treated with or complexed with Lewis acids. They are all acidicin their functionality as hydrocarbon conversion catalysts.

If a solid catalyst is used to promote the alkylation reaction in someembodiments, it may be introduced into vessel 10 via line 15, as anaqueous or nonaqueous slurry or stream. Alternatively, or additionally,catalyst may be added elsewhere in the system 1. For example, catalystslurry may be injected into line 21. In some embodiments, the catalystis added continuously to vessel 10 via line 15. Without wishing to belimited by theory, it is believed that sub-micron particles or bubblesdispersed in a liquid undergo movement primarily through Brownian motioneffects. The droplets in the product emulsion created by HSD 40 may havegreater mobility through boundary layers of solid catalyst particles,thereby facilitating and accelerating the catalytic reaction throughenhanced transport of reactants.

A stream of concentrated liquid acid is introduced into line 21, and ispumped through line 13 into HSD 40. In line 13, the acid mixture iscombined with a liquid hydrocarbon introduced into line 13 via line 22.Alternatively, the hydrocarbon may be fed directly into HSD 40, orcombined with acid upstream of pump 5 rather than being combined withthe acid in line 13. Pump 5 is operated to pump the acid through line21, and to build pressure and feed HSD 40, providing a controlled flowthroughout high shear mixer (HSD) 40 and system 100. In someembodiments, pump 5 increases the pressure of the HSD inlet stream togreater than 345 kPa (50 psig). In some embodiments, pump 5 increasesthe pressure of the stream to greater than 3447 kPa (500 psig). In someembodiments, pump 5 increases the pressure of the stream to greater than202.65 kPa (29 psig) or greater than about 303.975 kPa (44 psig). Inthis way, high shear system 100 may combine high shear with pressure toenhance reactant intimate mixing of the reaction mixture.

In this manner, external high shear device 40 produces an emulsion ofdispersible reactant from line 22 within continuous phase introduced vialine 21.

In contrast to other systems, the presently disclosed high shear system100 comprises an enclosed external high shear mixing device 40 to createan emulsion (and/or submicron-sized globules) of hydrocarbon in acidcatalyst (or acid catalyst in hydrocarbon). As discussed in detailhereinabove, external high shear device 40 is a mechanical device thatutilizes, for example, a stator rotor mixing head with a fixed gapbetween the stator and rotor. Dispersible catalyst and liquidhydrocarbons are introduced separately or as a mixed stream into HSD 40.Mixing results in an emulsion of dispersible catalyst in micron or submicron droplet sizes. Therefore, high shear mixer outlet line 18comprises an emulsion of micron and/or submicron-sized globules, asdiscussed hereinabove.

In some embodiments, hydrocarbon feed is continuously fed into line 13to form the feed stream to HSD 40. Water may also be introduced with theacid, or it may be introduced independently. The actual ratio of rawmaterials depends on the desired selectivity and operating temperaturesand pressures.

After pumping, the hydrocarbon and acid reactants are mixed within HSD40, which serves to create a fine dispersion or emulsion of thehydrocarbon in the concentrated acid mixture. In HSD 40, the hydrocarbonand the concentrated acid catalyst are highly dispersed such that anemulsion is formed. The emulsion may be a nonaemulsion. An emulsion ornanoemulsion is sometimes also referred to herein as a “dispersion.” Forthe purposes of this disclosure, a nanoemulsion is an emulsion ofimmiscible liquid phases in which the sizes of the droplets (globules)in the dispersed phase are less than 1000 nanometers (i.e., <1 micron).For example, disperser IKA® model DR 2000/4, a high shear, three stagedispersing device configured with three rotors in combination withstators, aligned in series, is used to create the emulsion ofhydrocarbon in the liquid medium comprising the concentrated acidcatalyst. The rotor/stator sets may be configured as illustrated in FIG.2, for example. The combined reactants enter the high shear mixer vialine 13 and enter a first stage rotor/stator combination havingcircumferentially spaced first stage shear openings. The coarse emulsionexiting the first stage enters the second rotor/stator stage, havingsecond stage shear openings. The reduced droplet-size emulsion emergingfrom the second stage enters the third stage rotor/stator combinationhaving third stage shear openings. The emulsion exits the high shearmixer via line 18. In some embodiments, the shear rate increasesstepwise longitudinally along the direction of the flow. For example, insome embodiments, the shear rate in the first rotor/stator stage isgreater than the shear rate in subsequent stage(s). In otherembodiments, the shear rate is substantially constant along thedirection of the flow, with the stage or stages being the same. If thehigh shear mixer includes a PTFE seal, for example, the seal may becooled using any suitable technique that is known in the art. Forexample, the reactant stream flowing in line 13 may be used to cool theseal and in so doing be preheated as desired prior to entering the highshear mixer.

The rotor of HSD 40 is set to rotate at a speed commensurate with thediameter of the rotor and the desired tip speed. As described above, thehigh shear mixer (e.g., colloid mill) has either a fixed clearancebetween the stator and rotor or has adjustable clearance. HSD 40 servesto intimately mix the hydrocarbon and the concentrated acid. In someembodiments of the process, the transport resistance of the reactants isreduced by operation of the high shear mixer such that the velocity ofthe reaction is increased by greater than a factor of about 5. In someembodiments, the velocity of the reaction is increased by at least afactor of 10. In some embodiments, the velocity is increased by a factorin the range of about 10 to about 100 fold. In some embodiments, HSD 40delivers at least 300 L/h with a power consumption of 1.5 kW at anominal tip speed of at least 22.9 m/s (4500 ft/min), and which mayexceed 40 m/s (7900 ft/min) In some embodiments, the mixture issubjected to a shear rate greater than 20,000 s⁻¹.

Although measurement of instantaneous temperature and pressure at thetip of a rotating shear unit or revolving element in HSD 40 isdifficult, it is estimated that the localized temperature seen by theintimately mixed reactants is in excess of 500° C. and at pressures inexcess of 500 kg/cm² under cavitation conditions. The high shear mixingresults in formation of an emulsion or nanoemulsion in which thedispersed hydrocarbon-containing droplets/globules are micron orsubmicron-sized particles (i.e., mean diameter less than one micron). Insome embodiments, the resultant emulsion has an average droplet sizeless than about 1.5 μm. In some embodiments, the mean droplet size is inthe range of about 0.4 μm to about 1.5 μm. In some embodiments, theemulsion is a nanoemulsion in which the mean diameter of the droplets isless than 1 micron in size. In some embodiments, the mean droplet sizeis less than about 400 nm, in the range of about 200 nm to about 400 nm,or may be about 100 nm in some cases. Accordingly, the emulsion exitingHSD 40 via line 18 comprises micron and/or submicron-sized droplets. Inmany embodiments, the emulsion is able to remain dispersed atatmospheric pressure for at least 15 minutes.

Once dispersed, the resulting emulsion exits HSD 40 via line 18 andfeeds into vessel 10, as illustrated in FIG. 1. Alkylation ofisoparaffin will occur whenever suitable time, temperature and pressureconditions exist. In this sense the reaction may occur at any point inthe path between HSD 40, vessel 10 and pump 5, as shown in FIG. 1, ifthe temperature and pressure conditions are favorable. As a result ofthe intimate mixing of the reactants prior to entering vessel 10, asignificant portion of the chemical reaction may take place in HSD 40. Adiscrete reactor is usually desirable, however, to allow for increasedagitation and heating and/or cooling of the bulk reactants, andincreased residence time, if applicable. Accordingly, in someembodiments, vessel 10 may be used primarily for initial introduction ofcatalyst and/or separation of product. Alternatively, or additionally,vessel 10 may serve as a primary reaction vessel where most or someportion of the total alkylate product is produced. In either case, thechemical reaction comprises a liquid-liquid (or liquid/liquid/solid orliquid/solid in the presence of solid catalyst) reaction in which thereactants are in the form of a very fine emulsion. The reactants (i.e.,hydrocarbon and acid) comprise a two phase emulsion, or nanoemulsion.

The particular operating conditions used in the present process willdepend on the specific alkylation reaction being effected. Processconditions such as temperature, pressure, space velocity and molar ratioof the reactants will effect the characteristics of the resultingalkylate, and may be adjusted within the disclosed ranges by thoseskilled in the art with only minimal trial and error.

The bulk or global operating temperature of the reactants is desirablymaintained below their flash points. The temperature and pressure of thehigh shear system 100 vary depending on the feed, the type of catalystemployed, and the degree of alkylation sought in the process. Typically,the alkylation is carried out at mild temperatures. Industrialalkylation processes have historically used hydrofluoric or sulfuricacid catalysts under relatively low temperature conditions. The sulfuricacid alkylation reaction is particularly sensitive to temperature, withlow temperatures being favored to minimize the side reaction of olefinpolymerization.

The present alkylation process is suitably conducted at temperatures offrom about −40° C. to about 500° C., preferably from below about 40° C.to avoid undesirable side reactions, and most preferably from about 0°C. to about 20° C. In embodiments, the alkylation is carried out attemperatures of from about 0° C. to about 30° C. In embodiments, thealkylation is carried out at temperatures of from about 0° C. to about90° C. Lower reaction temperatures are preferred to maximize alkylateoctane.

Operating pressure is controlled to maintain the reactants in the liquidphase, and is suitably from about 345 kPa (50 psig) to about 34.5 MPa(5000 psig), preferably from about 345 kPa (50 psig) to about 10.3 MPa(1500 psig), and more preferably from about 552 kPa (80 psig) to about1379 kPa (200 psig). Weight hourly space velocity ranges from about 0.01hr⁻¹ to about 100 hr⁻¹ based on total olefin feed to the reaction zone.The most preferred weight hourly space velocity varies within this rangeas a function of reaction temperature and feedstock composition. Weighthourly space velocity may be readily optimized to attain a desiredoctane specification with minimal trial and error.

The emulsion may be further processed prior to entering vessel 10, ifdesired. The contents of vessel 10 are stirred continuously orsemi-continuously, the temperature of the reactants is controlled (e.g.,using a heat exchanger), and the fluid level inside vessel 10 isregulated using standard techniques. Alkylate may be produced eithercontinuously, semi-continuously or batch wise, as desired. Any reactiongas that is produced may exit reactor 10 via a gas line 17. This gasstream may comprise volatile products, for example. The gas removed vialine 17 may be further treated and vented, or the components may berecycled, as desired.

The reaction product stream comprising non-converted liquid hydrocarbon,alkylate, and any derivatives and byproducts exits vessel 10 by way ofline 16. The alkylate product may comprise a mixture of high-octane,branched paraffinic hydrocarbons. In embodiments, the alkylate comprisesprimarily isopentane and isooctane. In embodiments, alkylate productstream in line 16 may be suitable as a premium gasoline blendstock withantiknock and clean-burning properties. Upon removal from the reactor10, product in line 16 may be passed to a product upgrade system forfurther processing, as known to those of skill in the art.

In embodiments, as shown in FIG. 1, product in line 16 is introduced toliquid-liquid separator 30. Separator 30 may be, for example, a decanteror settling tank. In separator 30, the denser liquid acid alkylationcatalyst rapidly migrates to the bottom of the separator, while thealkylate product and unreacted hydrocarbon floats to the top of thesettler. The liquid catalyst 38 is withdrawn from the bottom of thesettler, and may be disposed via spent acid line 37 and/or introducedvia line 39 into fresh catalyst line 21 for reintroduction to HSD 40. Aportion of the catalyst liquid may be continuously or intermittentlywithdrawn from high shear system 100 via, for example, spent acid line37, for treatment in a regeneration facility or disposal in suitablefacilities (not shown).

Catalyst to be recycled may be regenerated prior to introduction intoline 21. For example, in embodiments, catalyst in line 38 flows tocatalyst cooler (not shown in FIG. 1) before being returned to highshear system 100. The alkylation reaction is typically exothermic, andfor this reason, the catalyst may be precooled before it is returned toHSD 40 to maintain the alkylation reaction temperature within thepreferred range. As noted above, temperature control in the alkylationreaction zone affects alkylate quality and is therefore an importantprocess control consideration. A suitable cooling medium withdraws heatfrom the liquid acid catalyst, preferably by indirectly contacting thecatalyst solution as the cooling medium flows through tubes of ashell-and-tube heat exchanger. Any suitable cooling medium known tothose skilled in the art may be employed, for example, chilled water ora solution of ethylene glycol in water.

The lighter hydrocarbon phase contained in the alkylation reactoreffluent charged to separator 30 readily forms a discrete hydrocarbonphase in the upper section of the separator 30. This hydrocarbon phaseincluding not only alkylated product but also unreacted hydrocarbon aswell as small amounts of acid catalyst, is withdrawn from separator 30via product line 35. The alkylate product may be piped to adeacidification step, for example, a caustic scrubber where thehydrocarbon product contacts an aqueous caustic solution (NaOH) toremove residual acid. Because the hydrocarbon phase and the aqueouscaustic phase are substantially immiscible, the two liquids are readilyseparated, with spent caustic and (substantially) acid-free hydrocarbonbeing withdrawn via separate streams from the deacidification vessel.

The catalyst-removed product 35 may be subjected to further processingand a portion of line 35 may be recycled. For example, high shear system100 may further comprise a depropanizer (not shown in FIG. 1) from whichpropane may be removed for resale or use as fuel, and/or adeisobutanizer (not shown in FIG. 1) from which isobutane may beremoved. A portion of recovered unconverted isobutane may be recycled tohigh shear device 40, for example, via recycle isoparaffin line 20. Thedeisobutanizer and depropanizer separators may comprise any suitableseparation means known to those skilled in the art, for example,conventional multiple tray fractionation towers with reboilers andoverhead condensers.

In embodiments, the acid catalyst comprises solid acid catalystsparticularly zeolites or aluminas which have been treated with Lewisacids, and alkylation produces what appears to be a low level polymer oroligomer. In such embodiments, solvent extraction may be used to removethese side products.

Multiple Pass Operation. Referring still to FIG. 1, the system isconfigured for single pass or multipass, wherein, after introduction ofthe liquid reactants and commencement of the process, the output fromline 16 of vessel 10 goes directly to recovery of the alkylate or tofurther processing. In some embodiments it may be desirable to pass thecontents of line 16, or a liquid fraction thereof, through HSD 40 duringa second pass. In this case, at least a portion of the product in line16 may be returned to HSD 40, with or without intervening processing,for further emulsification and reaction. Additional acid or water may beinjected via line 21 into line 13, or it may be added directly into thehigh shear mixer (not shown), if needed.

In some embodiments, two or more high shear devices like HSD 40, or theymay be configured differently, are aligned in series, and are used tofurther enhance the reaction. Their operation may be in either batch orcontinuous mode. In some instances in which a single pass or “oncethrough” process is desired, the use of multiple high shear devices inseries may also be advantageous. In some embodiments where multiple highshear devices are operated in series, vessel 10 may be omitted. Whenmultiple high shear devices 40 are operated in series, additionalreactant(s) may be injected into the inlet feed stream of each device.In some embodiments, multiple high shear devices 40 are operated inparallel, and the outlet emulsions therefrom are introduced into one ormore vessel 10.

In embodiments, use of the disclosed system and process comprisingreactant mixing via external high shear device 40 allows use of lessacid catalyst and/or excess of isoparaffin in high shear system 100 thanpreviously permitted. In embodiments, an external high shear device 40is incorporated into an established process thereby permitting anincrease in production (greater throughput) from a process operatedwithout high shear device 40. In embodiments, much of the reactionoccurs within the external high shear device 40. In embodiments, usageof catalyst is reduced when compared to alkylation in the absence ofexternal high shear device 40. In embodiments, the amount of olefinexcess is reduced when compared to alkylation in the absence of highshear device 40.

In embodiments, the system and process of the present disclosure providefor a higher alkylate yield from an isoparaffin feedstock thanconventional alkylation systems and processes comprising an absence ofexternal high shear mixing. In embodiments, the high shear alkylationsystem and process of the present disclosure allows the production of analkylate having a higher octane rating than alkylate obtained from analkylation reactor in the absence of high shear device 40. Inembodiments, the use of the present system and method for the alkylatingof isoparaffins makes economically feasible the use of reduced amountsof olefin and/or catalyst by increasing the rate of alkylation, etc.

In some embodiments, the enhanced mixing potentiates an increase inthroughput of the process stream. In contrast to some existing methodsthat attempt to increase the degree of alkylation by increasing reactorpressures, the superior dissolution and/or emulsification provided byexternal high shear dispersion may allow in many cases a decrease inoverall operating pressure while maintaining or even increasing reactionrate. Without wishing to be limited to a particular theory, it isbelieved that the level or degree of high shear mixing is sufficient toincrease rates of mass transfer and may also produce localized non-idealconditions that permit reactions to occur that might not otherwise beexpected to occur based on Gibbs free energy predictions. Localized nonideal conditions are believed to occur within the high shear deviceresulting in increased temperatures and pressures with the mostsignificant increase believed to be in localized pressures. The increasein pressures and temperatures within the high shear device areinstantaneous and localized and quickly revert back to bulk or averagesystem conditions once exiting the high shear device. In some cases, thehigh shear mixing device induces cavitation of sufficient intensity todissociate one or more of the reactants into free radicals, which mayintensify a chemical reaction or allow a reaction to take place at lessstringent conditions than might otherwise be required. Cavitation mayalso increase rates of transport processes by producing local turbulenceand liquid micro-circulation (acoustic streaming). An overview of theapplication of cavitation phenomenon in chemical/physical processingapplications is provided by Gogate et al., “Cavitation: A technology onthe horizon,” Current Science 91 (No. 1): 35-46 (2006). The high shearmixing device of certain embodiments of the present system and methodsis operated under what is believed to be cavitation conditions effectiveto dissociate the reactants into free radicals which then form intoalkylate product.

In some embodiments, the system and processes described herein permitdesign of a smaller and/or less capital intensive process thanpreviously possible without the use of external high shear mixer 40.Potential advantages of certain embodiments of the disclosed processesare reduced operating costs and increased production from an existingprocess. Certain embodiments of the disclosed processes additionallyoffer the advantage of reduced capital costs for the design of newprocesses. Potential benefits of some embodiments of this system andmethods for alkylation include, but are not limited to, faster cycletimes, increased throughput, higher conversion, reduced operating costsand/or reduced capital expense due to the possibility of designingsmaller reactors and/or operating the alkylation process at lowertemperature and/or pressure.

While preferred embodiments of the invention have been shown anddescribed, modifications thereof can be made by one skilled in the artwithout departing from the spirit and teachings of the invention. Theembodiments described herein are exemplary only, and are not intended tobe limiting. Many variations and modifications of the inventiondisclosed herein are possible and are within the scope of the invention.Where numerical ranges or limitations are expressly stated, such expressranges or limitations should be understood to include iterative rangesor limitations of like magnitude falling within the expressly statedranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4,etc.; greater than 0.10 includes 0.11, 0.12, 0.13, and so forth). Use ofthe term “optionally” with respect to any element of a claim is intendedto mean that the subject element is required, or alternatively, is notrequired. Both alternatives are intended to be within the scope of theclaim. Use of broader terms such as comprises, includes, having, etc.should be understood to provide support for narrower terms such asconsisting of, consisting essentially of, comprised substantially of,and the like.

Accordingly, the scope of protection is not limited by the descriptionset out above but is only limited by the claims which follow, that scopeincluding all equivalents of the subject matter of the claims. Each andevery claim is incorporated into the specification as an embodiment ofthe present invention. Thus, the claims are a further description andare an addition to the preferred embodiments of the present invention.The disclosures of all patents, patent applications, and publicationscited herein are hereby incorporated by reference, to the extent theyprovide exemplary, procedural or other details supplementary to thoseset forth herein.

What is claimed is:
 1. A method for alkylating a hydrocarbon comprisingat least one isoparaffin and at least one olefin, the method comprising:introducing a liquid catalyst selected from the group consisting ofhydrofluoric acid, BF₃, SbF₅, and AlCl₃, and combinations thereof andthe hydrocarbon into a high shear device, wherein the high shear devicecomprises a rotor and a stator separated by a shear gap; processing theliquid catalyst and the hydrocarbon in the high shear device to form anemulsion comprising droplets of hydrocarbon dispersed in the liquidcatalyst, wherein the droplets have a mean diameter in the range ofabout 0.1 μm to about 5 μm; introducing the emulsion into a vesseloperating under suitable alkylation conditions whereby at least aportion of the isoparaffin is alkylated with the olefin to formalkylate, wherein suitable alkylation conditions comprise a bulkreaction temperature of from about 38° C. to about 90° C. and a bulkreaction pressure in the range of from about 1379 kPa to about 34 MPa;and removing a product stream comprising alkylate from the vessel. 2.The method of claim 1, wherein the at least one isoparaffin containsfrom 4 to 8 carbon atoms.
 3. The method of claim 2, wherein the at leastone olefin contains from 2 to 12 carbon atoms.
 4. The method of claim 3,wherein the at least one isoparaffin is isobutane and the at least oneolefin is butene.
 5. The method of claim 1, wherein the droplets have amean diameter of no more than 100 nm.
 6. The method of claim 1, whereinforming the emulsion comprises subjecting the hydrocarbon and acid tohigh shear mixing at a tip speed of at least 22.9 m/s and to a shearrate of greater than about 20,000 s⁻¹, and wherein the high shear deviceproduces a local pressure of at least about 1034 MPa at the tip.
 7. Themethod of claim 1, wherein the shear gap has a width in the range offrom about 0.02 mm to about 5 mm, and wherein the rotor and the statoreach comprise at least one toothed surface.
 8. A method for alkylating ahydrocarbon comprising at least one isoparaffin and at least one olefin,the method comprising: introducing a liquid catalyst selected from thegroup consisting of hydrofluoric acid, BF₃, SbF₅, AlCl₃, andcombinations thereof, and the hydrocarbon into a high shear devicecomprising at least one rotor and at least one stator separated by ashear gap width; processing the liquid catalyst and the hydrocarbon inthe high shear device to form an emulsion comprising droplets having amean diameter less than about 5 μm; and transferring the emulsion fromthe high shear device into a vessel operating under suitable alkylationconditions whereby at least a portion of the isoparaffin is alkylatedwith the olefin to form alkylate.
 9. The method of claim 8, wherein theat least one isoparaffin contains from 4 to 8 carbon atoms.
 10. Themethod of claim 9, wherein the at least one olefin contains from 2 to 12carbon atoms.
 11. The method of claim 10, the method further comprisingremoving a product stream comprising alkylate from the vessel, whereinthe droplets have a mean diameter of no more than 100 nm.
 12. The methodof claim 10, wherein the shear gap is in the range of from about 0.02 mmto about 5 mm, and wherein the rotor and the stator each comprise atleast one toothed surface.
 13. The method of claim 10, wherein theemulsion comprises hydrocarbon droplets dispersed in the liquidcatalyst, and wherein the mean diameter is less than 1 micron.
 14. Themethod 10, wherein the emulsion comprises catalyst droplets dispersed inthe hydrocarbon, and wherein the mean diameter is less than 1 micron.15. The method of claim 10, wherein the mean diameter is also greaterthan about 0.1 μm.
 16. A method for alkylating a hydrocarbon comprisingat least one isoparaffin and at least one olefin, the method comprising:introducing a liquid catalyst and the hydrocarbon into a high sheardevice comprising at least one rotor and at least one stator separatedby a shear gap width, wherein the liquid catalyst comprises an acidselected from the group consisting of hydrofluoric acid, BF₃, SbF₅,AlCl₃, and combinations thereof; forming an emulsion comprisinghydrocarbon droplets dispersed in the liquid catalyst, wherein thedroplets have a mean diameter of less than about 5 μm; and introducingthe emulsion into a vessel operating under suitable alkylationconditions whereby at least a portion of the isoparaffin is alkylatedwith the olefin to form alkylate, wherein suitable alkylation conditionscomprise a bulk reaction temperature of from about 38° C. to about 90°C. and a bulk reaction pressure in the range of from about 1379 kPa toabout 34 MPa.
 17. The method of claim 16, wherein the mean diameter isalso greater than about 0.1 μm.